$ { \left[\begin{array}{rr}{-1} & {-2} \\ {-2} & {-1}\end{array}\right]-\left[\begin{array}{rr}{1} & {0} \\ {2} & {-1}\end{array}\right] = {?} } $
To find the difference of two matrices, subtract the corresponding items between each matrix. ${\left[\begin{array}{rr}{-1}-{1} & {-2}-{0} \\ {-2}-{2} & {-1}-{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{-2} & {-2} \\ {-4} & {0}\end{array}\right]}$